Any Plumbing/Heating peeps here

[TSM]

Right

im just having a Valliant 418 Heating boiler put in (open vented, S-plan). Its a straight swap from the old one to new one, some piping needs to be done, electrics are all ok. Now the issue is that the boiler needs the pump wired in to overrun when the timer (external) shuts the system down, when this happens the valves close but the boiler keeps the pump running, the installer wants to put a by-pass in, but without a auto by-pass valve, just from after the pump to the return flow.

I thought it needed a bypass valve so that the water only bypasses when the valves shut and the pump is in overrun, otherwise you will circulate hot water straight back to the return while its running. Granted he is installing the by-pass in with a smaller than 15mm, which would mean that the flow is mainly going to the heating.

I think hees a little confused as he mainly puts in system boilers and combi boilers and we are having a convential condensing heat only boiler.

[Flamin_Squirrel]

I deal more with the commercial side of things rather than domestic, but I'm not quite sure what you mean by 'system' shuts down. The pump needs to run on after the boiler shuts down to prevent the boiler over heating, no bypass required.

The only time you'd need a bypass is if you've got thermostatic radiator valves, so that if they all shut you've got some form of pressure relief. In that case a bypass, whether it's fitted with a valve or not, should do the trick.

[Foey]

The only time you'd need a bypass is if you've got thermostatic radiator valves, so that if they all shut you've got some form of pressure relief. In that case a bypass, whether it's fitted with a valve or not, should do the trick.

I thought you always had to have at least one radiator (usually bathroom) in the system that didn't have a thermostatic valve on it, that's what i was told just before i installed mine.

[kwak zzr]

I thought you always had to have at least one radiator (usually bathroom) in the system that didn't have a thermostatic valve on it, that's what i was told just before i installed mine.

tis correct.

[Flamin_Squirrel]

I thought you always had to have at least one radiator (usually bathroom) in the system that didn't have a thermostatic valve on it, that's what i was told just before i installed mine.

That's the alternative to having a bypass. A bypass will however save energy, being as you're not throwing heat out of a radiator just to allow water around the system.

[TSM]

I deal more with the commercial side of things rather than domestic, but I'm not quite sure what you mean by 'system' shuts down. The pump needs to run on after the boiler shuts down to prevent the boiler over heating, no bypass required.

The only time you'd need a bypass is if you've got thermostatic radiator valves, so that if they all shut you've got some form of pressure relief. In that case a bypass, whether it's fitted with a valve or not, should do the trick.

Well if you have the flow comming from the boiler, to the pump which then splits into 2 valves, one CH one HW, if they are both closed because the timer has turned off, the boiler keeps the pump running, it will be pumping nothing, so the by-pass is takes off between the pump output and the valves and goes to the return flow into the boiler, but when the system is running, you dont want any bypass to happen as the valves are open. So having an auto by-pass valve in the by-pass loop, it will open when the pressure diffirential changes between the flow & return loops.

Not sure if that makes sense.

[TSM]

I thought you always had to have at least one radiator (usually bathroom) in the system that didn't have a thermostatic valve on it, that's what i was told just before i installed mine.

we only have the bedrooms with TRVs, the rest of the rooms dont have them as they never get that hot

[gerbrox]

Well if you have the flow comming from the boiler, to the pump which then splits into 2 valves, one CH one HW, if they are both closed because the timer has turned off, the boiler keeps the pump running, it will be pumping nothing, so the by-pass is takes off between the pump output and the valves and goes to the return flow into the boiler, but when the system is running, you dont want any bypass to happen as the valves are open. So having an auto by-pass valve in the by-pass loop, it will open when the pressure diffirential changes between the flow & return loops.

Not sure if that makes sense.


Okay you'll need a bypass pressure relief controler as if you don't then the pump wil be pumping against a closed head and will eventually knacker the pump. The pump will run on to disapate the heat, as an alternative can the guy not link out the run on timer so that the pump will cwitch off when the timer goes off. The valves (2-ports I assume) will not just close striaght away they'll probably take 10 -15 secs or so.

[TSM]

Okay you'll need a bypass pressure relief controler as if you don't then the pump wil be pumping against a closed head and will eventually knacker the pump. The pump will run on to disapate the heat, as an alternative can the guy not link out the run on timer so that the pump will cwitch off when the timer goes off. The valves (2-ports I assume) will not just close striaght away they'll probably take 10 -15 secs or so.

hBefore i had wired the system so the timer controled the pump, but now as its a new Vaillent 418 condensing boiler, the pump has been removed from crontrol of the timer to control of the boiler (wired direct to the boiler circuit board), the boiler has a perm live so it can control the pump, ive gone into diag mode and it does not allow the pump overrun to be turned off, only decreased to 2mins. The valves flip the micro switch within 2s of the power being cut to the servo.

The way he has put the bypass loop in, when its open ive noticed that it keeps the boiler temp too high and it throttles the output to maintain a 75c water temp and the rad temp starts to go down. At the moment, as the timer is perm on ive shut the by-pass so it heats the house faster as its had no heating for the last 5 days. The loop has a ball stop valve on it, so i was thinking of removing it myself and putting in a by-pass valve, problem is i mayl have to drain the system, unless i just shut the valve and then cut more pipe and put it between the pump and ball valve. Other problem, is he has put the by-pass pipe as 15mm but i can only find 22mm by-pass valves.

Hees in tommorow, so i may just be insistant and get him to put it in when he drains the system again.

Im not an installer, but i know how to read manuals and have a good understanding of how it all works.

[Rich]

Right

im just having a Valliant 418 Heating boiler put in (open vented, S-plan). Its a straight swap from the old one to new one, some piping needs to be done, electrics are all ok. Now the issue is that the boiler needs the pump wired in to overrun when the timer (external) shuts the system down, when this happens the valves close but the boiler keeps the pump running, the installer wants to put a by-pass in, but without a auto by-pass valve, just from after the pump to the return flow.

I thought it needed a bypass valve so that the water only bypasses when the valves shut and the pump is in overrun, otherwise you will circulate hot water straight back to the return while its running. Granted he is installing the by-pass in with a smaller than 15mm, which would mean that the flow is mainly going to the heating.

I think hees a little confused as he mainly puts in system boilers and combi boilers and we are having a convential condensing heat only boiler.

He's installing the bypass the old fasion way. We remove alot of gate valves and ball valves now and replace them with a auto bypass that works on pressure, they should be 22mm really so the flow rate will remain the same with the valve open thus lowering the temp on pump over run quicker..

It needs this to prevent the pump from pumping hot water nowhere.. Like has been said in theory all of your rads could have TRV's on and they could all shut down, if this happens then theres nowhere for the water to go. The bypass should be set to prevent it opening on normal operating temperatures, it should only open if the pressure increases i.e because the valves have shut.

Good boiler the Vaillant thats all we fit and have only had a hand full of problems on the thousands we fit.. 2 years warrenty too i think with yours, their customer service is very good!!!

Oh and make sure he balances the system too, i.e turning down the rads that get hottest first to throw some of that heat to the other buggers rads perhaps!!!

Hope im helping in some way!! :D

~Rich~

[TSM]

He's installing the bypass the old fasion way. We remove alot of gate valves and ball valves now and replace them with a auto bypass that works on pressure, they should be 22mm really so the flow rate will remain the same with the valve open thus lowering the temp on pump over run quicker..

It needs this to prevent the pump from pumping hot water nowhere.. Like has been said in theory all of your rads could have TRV's on and they could all shut down, if this happens then theres nowhere for the water to go. The bypass should be set to prevent it opening on normal operating temperatures, it should only open if the pressure increases i.e because the valves have shut.

Good boiler the Vaillant thats all we fit and have only had a hand full of problems on the thousands we fit.. 2 years warrenty too i think with yours, their customer service is very good!!!

Oh and make sure he balances the system too, i.e turning down the rads that get hottest first to throw some of that heat to the other buggers rads perhaps!!!

Hope im helping in some way!! :D

~Rich~

Its been a nightmare week, old boiler (Concord 255, 25yrs old) was condemmed on tuesday, got some quotes, got guy to start on monday, got some goods, he got some money then just disapeared, lucly it was just a little more than the cost of the goods. I found some good guy from the Corgi website that was able to come and start on sunday, fraction of the cost of everyone else.

Even though i had 7 TRVs to install, he recomended to only install them in the bedrooms (3) as the living room and everywhere never gets hot enough to need us to turn the temp down, i will need to change the rads soon anyway along with the hot water cylinder as its not foam insulated, just blanket.

Ile try and insist to him that he should put in a 22mm bypass and put the valve, otherwise ile have to do it myself.

[Rich]

Even though i had 7 TRVs to install, he recomended to only install them in the bedrooms (3) as the living room and everywhere never gets hot enough to need us to turn the temp down, i will need to change the rads soon anyway along with the hot water cylinder as its not foam insulated, just blanket.

Ile try and insist to him that he should put in a 22mm bypass and put the valve, otherwise ile have to do it myself.

If only i was closer i'd come and do your rads, cylinder and bypass for you, tis a nice little job..

As for the TRV's he's talking poop, they shut down on air temp not water temp so even if you think the rads not very hot it could still be hot enough in the room for the TRV to shut down. Thats where the money saving comes in too your not heating any unwanted rooms. Plus if you have them on all you rads you can turn the TRV's down low in the rooms you don't use very much and up higher for the living room ect.. This helps to balance the system too keeping the rooms you want warm warmer than the ones you don't!! :D

[TSM]

If only i was closer i'd come and do your rads, cylinder and bypass for you, tis a nice little job..

As for the TRV's he's talking poop, they shut down on air temp not water temp so even if you think the rads not very hot it could still be hot enough in the room for the TRV to shut down. Thats where the money saving comes in too your not heating any unwanted rooms. Plus if you have them on all you rads you can turn the TRV's down low in the rooms you don't use very much and up higher for the living room ect.. This helps to balance the system too keeping the rooms you want warm warmer than the ones you don't!! :D

Yep i thought the same, but realy our living room never gets that warm, its 5x5x3m in size and open though to 2nd living room to aprox the same size. So the rads are always on and it never gets hot hot. There is 1 TRV, where i changed it myself.

As i said, ile need to change some of the rads as they are so old, no convectors, even the return temp of the water is high enough to not be using the full power of the 18kw boiler, and thats with all rads turned on in the house and its still not that hot. So ile add the remaining TRVs then.

Lots of insulation/upgrades to be done in this house. If i had all the tools, i would be doing most of the pipework myself, except for the gas.

[nakedblue650]

Auto hydraulic bypass required for 1) benefit of boiler & system 2) to comply with Building Regs Part 'L'.

As you have 18kw of available power it should be in 22mm.

Also you shouldn't have any rads on the primary circuit or acting as by pass (commonly mis-referred to as heat dump!).

Also if you have TRVs on all rads you obviously wouldnt have a room thermostat! Another fail! You need a room stat to comply with Building Regs again! So anyone who says otherwise is talking poop!

if you PM me I can e-mail a Part 'L' regs overview if you want it.

nb650

[TSM]

Auto hydraulic bypass required for 1) benefit of boiler & system 2) to comply with Building Regs Part 'L'.

As you have 18kw of available power it should be in 22mm.

Also you shouldn't have any rads on the primary circuit or acting as by pass (commonly mis-referred to as heat dump!).

Also if you have TRVs on all rads you obviously wouldnt have a room thermostat! Another fail! You need a room stat to comply with Building Regs again! So anyone who says otherwise is talking poop!

if you PM me I can e-mail a Part 'L' regs overview if you want it.

nb650

Yep i read about the 18+kw needing 22mm, plus "Part L" of regs. The rads are not in the by-pass circuit, its just between the pump and return flow.

[nakedblue650]

Have a look in the back of the installation manual at the Benchmark pages - it will tell you what is required to comply with Regs. Sooooo many people do not know what is and isnt required.

nb650

[gerbrox]

He's installing the bypass the old fasion way. We remove alot of gate valves and ball valves now and replace them with a auto bypass that works on pressure, they should be 22mm really so the flow rate will remain the same with the valve open thus lowering the temp on pump over run quicker..

It needs this to prevent the pump from pumping hot water nowhere.. Like has been said in theory all of your rads could have TRV's on and they could all shut down, if this happens then theres nowhere for the water to go. The bypass should be set to prevent it opening on normal operating temperatures, it should only open if the pressure increases i.e because the valves have shut.

Good boiler the Vaillant thats all we fit and have only had a hand full of problems on the thousands we fit.. 2 years warrenty too i think with yours, their customer service is very good!!!

Oh and make sure he balances the system too, i.e turning down the rads that get hottest first to throw some of that heat to the other buggers rads perhaps!!!

Hope im helping in some way!! :D

~Rich~


If the guy is worth he weight in gold he'll balance the system correctly, i.e. measuring the flow and return with an infra red gun and balancing the temperature so that all rads are 82 / 71 (regulating at the lockshields). he'll probably just vent all the rads andensure there all heating and leave. Also gethimto flush the other rads out as they sound as though there blocked full of sh1te andalso get himto fire some inhibitor in as well.

[gerbrox]

Auto hydraulic bypass required for 1) benefit of boiler & system 2) to comply with Building Regs Part 'L'.

As you have 18kw of available power it should be in 22mm.

Also you shouldn't have any rads on the primary circuit or acting as by pass (commonly mis-referred to as heat dump!).

Also if you have TRVs on all rads you obviously wouldnt have a room thermostat! Another fail! You need a room stat to comply with Building Regs again! So anyone who says otherwise is talking poop!

if you PM me I can e-mail a Part 'L' regs overview if you want it.

nb650


Does the Part L regs not just apply to commercial and also any new builds?

Might just be me, part L just hitting up here!!

[TSM]

If the guy is worth he weight in gold he'll balance the system correctly, i.e. measuring the flow and return with an infra red gun and balancing the temperature so that all rads are 82 / 71 (regulating at the lockshields). he'll probably just vent all the rads andensure there all heating and leave. Also gethimto flush the other rads out as they sound as though there blocked full of sh1te andalso get himto fire some inhibitor in as well.

The rads were not that bad, I flushed the system about 5/6 years ago (also replaced all the wiring) and put fernox in it. There is a little bit of, hees put in some cleaner today and tommorow he will flush it again and put inhibitor in.

Only issue has been the by-pass loop that ive not been happy with, everything else he has been good.

We will get there, slowly but surely.